M104 Mechanical Smog-Air pump delete - PeachParts Mercedes-Benz Forum

87tdwagen · #1 03-01-2020, 01:03 PM

Hi All,
I have been reading up on several posts regarding deleting the mechanical air pump on M104s due to pulley bearing etc. Many have gone the route of a simple delete and using a shorter belt.

I would be curious as to your long term experience going this way. Any noticeable negatives? Increased belt wear, idler pulley wear?

For any air-pump experts, I have another question regarding the clutch engagement. I have over the past few months the dreaded squeal at cold start-up for about a minute and then goes away syndrome, so it seems to indicate the pump bearing is going bad and the pulley bearing is fine as no noise from it after the first minute nor at speed.

Unplugged the clutch wire, still happens like clock work, cold start up 1 min screech then smooth?? Okay, remove the clutch plate assembly....Still happens, like clock work????? What could possibly be engaging with both the wire unplugged and clutch assembly (external) removed?

This one has stumped me, at first I thought friction possibly but the repeated timing of it cutting out leaves me wondering, unless that little bit of heat generated from friction is what causes it to free up a minute later.

Any ideas?

This is what's leading me down the delete path, at least to bench the pump and tear into it for a while.

TIA

speednjay · #2 03-01-2020, 02:25 PM

Probably the bearing on the clutch

87tdwagen · #3 03-02-2020, 02:36 PM

Good suggestion on the clutch bearing. Ive got the pump out and will take it apart and see what I find.

In the mean time for those interested in the shorter belt length 935K6 or 6PK935, 93.5 inches in length is a perfect fit, the 92.5 inch belt as in 6PK925 will also work but is tight and wont allow the tensioner to adjust much, so the 93.5 inch one works best and gives a normal tensioner adjustment range.

Yay, no more sequel

speednjay · #4 03-02-2020, 06:57 PM

I’ll take your old pump off your hands if your tossing it. I live in California. I need to have everything hooked up and working.

kwontumspeed · #5 03-03-2020, 07:56 AM

Can you explain how you are routing that on the M104 with the 93.5" ?

87tdwagen · #6 03-03-2020, 10:22 AM

Quote:

Originally Posted by speednjay

I’ll take your old pump off your hands if your tossing it. I live in California. I need to have everything hooked up and working.

Will keep that in mind, I plan on restoring it though and keeping with the car for now, if that changes, will send you a PM

87tdwagen · #7 03-03-2020, 10:30 AM

Quote:

Originally Posted by kwontumspeed

Can you explain how you are routing that on the M104 with the 93.5" ?

I cant seem to enlarge your attachment, but it looks like a common one, in which case my belt routing path is the one in the lower right sans the Air Pump #6 in the diagram.

The length will depend on your particular routing and accessories package, notably with or without AC, but I would imagine most US spec 1994-95 M104s in the E-class came with Air Cond and would have the belt configuration shown in the lower right quadrant. Later M104s have a slightly different layout and possibly an electric air pump rather than belt driven.

kwontumspeed · #8 03-03-2020, 10:34 AM

Quote:

Originally Posted by 87tdwagen

in which case my belt routing path is the one in the lower right sans the Air Pump #6 in the diagram.

Thanks, I'm an idiot, not enough coffee when I replied. I was trying to route the belt around the air pump pulley in the diagram still in place (with the ac) instead of removing it from the equation.

87tdwagen · #9 03-03-2020, 11:04 AM

I prefer coffee over both gas or diesel in the mornings too

Still curious as to others experience long term with the air pump removed, particularly on the idler pulley given the 90 degree angle the belt takes there vs a 45 degreeish angle that it had before. If anyone has any long term experience and can report back would be great, particularly if we need to plan to obtain future spares for replacement.

Thanks

engatwork · #10 03-03-2020, 07:50 PM

Years ago I had a guy bring me a early/mid 90's SL with the air pump removed and a idler type pulley mounted on a steel bracket they made to replace it. Seemed to work good.

kwontumspeed · #11 03-04-2020, 08:18 AM

Quote:

Originally Posted by 87tdwagen

I prefer coffee over both gas or diesel in the mornings too

Still curious as to others experience long term with the air pump removed, particularly on the idler pulley given the 90 degree angle the belt takes there vs a 45 degreeish angle that it had before. If anyone has any long term experience and can report back would be great, particularly if we need to plan to obtain future spares for replacement.

Thanks

The change isn't going to present that much more force/stress to make a difference on the bearings.

87tdwagen · #12 03-04-2020, 11:39 AM

So it appears the idler pulley will not be an issue, they also still seem readily available for replacement and fairly inexpensive, so no worries there. Thanks

Regarding the air pump, I managed to look at it more closely and it seems that one of the blades is slightly touching the inner hub. Both the pulley bearing is fine as well as the main pump bears as far as I can tell. No play, and no roughness, just the fan blade touching the inner cylinder wall in one spot. This was far more noticeable spinning it counter clockwise rather than the normal clockwise rotation.

I shot in some PB Blaster oil and spun the pump counter clockwise until I could no longer hear nor feel any hangup. When turning the pump over to drain out, most of the fluid was black, as in carbon soaked.

I assume that the exhaust check valve had a minor leak, not noticeable enough to leave an obvious sign on the tubing or exhaust port of the pump as they were clean with the exception of some carbon dust when wiping with a white towel, otherwise visually looked good.

The intake filter, while a little dirty on the outside was very clean on the inside, as was the intake chamber. Either way it seems some crud had accumulated over time and was sticking to the blade tips, causing the scraping, screeching.

Since it tested on a bench only with a power drill spinning the pump, I cant confirm completely, I'll have to get it back on the car to see of the belt tension and or rpms tell a different tale.

If you have some slight noises from your air pump, it may be worth taking it off and inspecting and cleaning before you go off to replace it, or worse, let it slide until you are forced to replace or remove it. Worth a shot.

You could use carb or brake cleaner, but if you have PB Blaster or liquid wrench, you'll get similar cleaning results and get some lube in there anyway, low risk to the internal bearing.

Diseasel300 · #13 03-04-2020, 12:50 PM

Not sure about the MB smog pump, but the Ford engine-driven pumps had carbon vanes in them. The black stuff that came out may have just been carbon dust, not exhaust soot.

87tdwagen · #14 03-04-2020, 10:09 PM

Quote:

Originally Posted by Diseasel300

Not sure about the MB smog pump, but the Ford engine-driven pumps had carbon vanes in them. The black stuff that came out may have just been carbon dust, not exhaust soot.

I think you're right on the carbon vanes.
There's some really good info and pjctures of all the pump internals disassembled and those vanes look like they're carbon to me.

w124 Smog Air Pump rebuild

Must have been carbon dust buildup on either the blade ends or cylinder walls leading to the scraping in my case.

rayhennig · #15 03-08-2020, 03:20 AM

I recall people saying that they had found the correct bearing in the USA and replaced that to give the pump a new lease of life.

In my case, I found a brand new pump for sale in Greece and bought it for around 230€. When it arrived, it turned out to be almost exactly right aside from a deeper pulley with more grooves - from a V12, I think. Anyway, once installed, with the belt using all but one or two of the grooves, all is now well. Although the clearance is pretty small with the deeper pulley!

RayH